Question

I have a situation I don´t know how to model correctly. I want every child of a class to be associated with a media object (photo, video or music). I want to know which is the preffered approach to this problem. What I have right now is:

class Something(models.Model):

    media = models.ForeignKey(Media)


class Media(models.Model):
    title = models.CharField(max_lenght=100)
    def get_tiny_object():
        pass
    def get_big_object():
        pass

class Picture(Media):
    picture = models.ImageField()
    def get_tiny_object():
        return ...
    ...

class Video(Media):
    video = models.CharField(max_length=200) #youtube id
    ...

class Music(Media):
    music = ....

You get the idea. ¿Does this work? Should I also record on “Something” what kind of media it is?

EDIT:

The idea behind having a Media class, is that I can render in the templates without knowing which kind of media I´m rendering. get_tiny_object() should return, if it is a picture:

"<img style="width:60px; height: 50px" ...>"

So if I have a foreign key to a media object lets say it’s id=4, does django know that it should be fetched from music table, if the object I associated with is of Music kind? Because I´ll have 3 different id=4, one on each table (picture, video and music (and possibly more if the domain changes)).

Answer 1

I still think the question is a little hard to understand – the title is Database modelling in Django after all…However, this is a perfectly valid and reasonable thing to do, and seems to fit your intent:

The recommended way to do this is multi table inheritance – example:

class Media(models.Model):
    pass

class Something(models.Model):
    media = models.ForeignKey(Media)

class Picture(Media):
    foo = models.CharField(max_length=100)

    def get_tiny_object(self):
        return self.foo

class Video(Media):
    bar = models.CharField(max_length=100)

    def get_tiny_object(self):
        return self.bar

picture = Picture.objects.create(foo='some picture')
video = Video.objects.create(bar='some video')
something1 = Something.objects.create(media=picture)
something2 = Something.objects.create(media=video)
print something1.media.get_tiny_object() # this is a picture remember?
print something2.media.get_tiny_object() # and lo, here is a video